Reducing power dissipation in driver circuits

ABSTRACT

In one example, a method includes generating, by a current source of a device, a first portion of a power signal that drives one or more load elements. In this example, a second portion of the power signal is generated by one or more components that are external to the device and are in parallel to the current source such that the second portion of the power signal does not flow through the current source.

This application is a continuation application of U.S. patentapplication Ser. No. 15/087,062, filed on Mar. 31, 2016, the entirecontents of which are incorporated by reference.

TECHNICAL FIELD

This disclosure relates to reducing the amount of power dissipated indriver circuits, and in particular, to using one or more low-costcomponents to reduce the amount of power dissipated in driver circuits.

BACKGROUND

Driver circuits may be used to control the amount of power provided toloads from power sources. In operation, a driver circuit may dissipatean amount of power that is proportional to the voltage across the drivercircuit and the current flowing through the driver circuit. In someexamples, such power dissipation may cause a driver circuit to overheat,which may negatively impact the functionality of the driver circuit. Assuch, in some examples, it may be desirable to reduce the amount ofpower dissipated by driver circuits.

SUMMARY

In general, this disclosure is directed to reducing the amount of powerdissipated in driver circuits. For example, a system may include one ormore external components in parallel with a current source of a driverdevice to reduce amount of power dissipated in the driver device.

As one example, a method includes generating, by a current source of adevice, a first portion of a power signal that drives one or more loadelements, wherein a second portion of the power signal is generated byone or more components that are external to the device and are inparallel to the current source such that the second portion of the powersignal does not flow through the current source.

As another example, a driver device includes a current source configuredto generate a first portion of a power signal that drives one or moreload elements, wherein a second portion of the power signal is generatedby one or more components that are external to the device and are inparallel to the current source such that the second portion of the powersignal does not flow through the current source.

As another example, a driver device includes means for generating afirst portion of a power signal that drives one or more load elements,wherein a second portion of the power signal is generated by one or morecomponents that are external to the device and are in parallel to thecurrent source such that the second portion of the power signal does notflow through the current source; and means for outputting the firstportion of the power signal.

The details of one or more examples of the disclosure are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages will be apparent from the description anddrawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A-1D are a conceptual diagrams illustrating example systems thateach include a driver device configured to drive a load with a powersignal, in accordance with one or more exemplary techniques of thisdisclosure.

FIG. 2 is a conceptual diagram illustrating an example system thatincludes a plurality of driver devices configured to collectively drivea load with a power signal, in accordance with one or more exemplarytechniques of this disclosure.

FIG. 3 is a conceptual diagram illustrating an example system thatincludes a driver device and one or more passive elements configured tocollectively drive a load with a power signal, in accordance with one ormore exemplary techniques of this disclosure.

FIG. 4 is a conceptual diagram illustrating an example system thatincludes a driver device and one or more passive elements configured tocollectively drive a load with a power signal, in accordance with one ormore exemplary techniques of this disclosure.

FIG. 5 is a conceptual diagram illustrating an example system thatincludes a driver device and one or more passive elements configured tocollectively drive a load with a power signal, in accordance with one ormore exemplary techniques of this disclosure.

FIG. 6 is a conceptual diagram illustrating an example system thatincludes a driver device and one or more passive elements configured tocollectively drive a load with a power signal, in accordance with one ormore exemplary techniques of this disclosure.

FIG. 7 is a graph illustrating example current levels in a system thatincludes a driver device and one or more passive elements configured tocollectively drive a load with a power signal, in accordance with one ormore exemplary techniques of this disclosure.

FIG. 8 is a conceptual diagram illustrating an example system thatincludes a multi-channel driver device and a plurality of passiveelements configured to collectively drive a plurality of loads with aplurality of power signals, in accordance with one or more exemplarytechniques of this disclosure.

FIG. 9 is a schematic diagram illustrating an example load 6 that may bedriven using a power signal generated by a driver device and one or morepassive elements in parallel with the driver device, in accordance withone or more techniques of this disclosure.

FIG. 10 is a flow diagram illustrating an example technique reducing thepower dissipation of a driver device, in accordance with one or moretechniques of this disclosure.

DETAILED ABSTRACT OF THE INVENTION

In general, this disclosure is directed to reducing the amount of powerdissipated in driver circuits. As discussed above, driver circuits maycontrol the amount of power provided to loads from power sources. Insome examples, the power source may be a variable power source, such asa battery with an operating voltage range of 8 volts (V) to 18V. As thepower dissipated by a driver circuit increases in proportion to thevoltage across the driver circuit and excess power dissipation maynegatively impact the functionality of the driver circuit, it may bedesirable for the driver circuit to be able to dissipate the “worstcase” amount of power without negatively impacting the functionality ofthe driver circuit. In some examples, the functionality of the drivercircuit may be negatively impacted if the power dissipated by the drivercircuit causes a temperature of the driver circuit (e.g., a junctiontemperature) to exceed a threshold (e.g., 50° C., 100° C., 150° C., 200°C.).

In some examples, the amount of power dissipated in a driver circuit maybe reduced through the use of a ballast regulator in which power isdistributed in a series element and regulated via a loop. In someexamples, the stability of the regulation loop in such a circuit mayhave the same characteristics and drawbacks as a low-drop out voltageregulator. In some examples, external transistors may also be used inthe regulation loop.

In other examples, the amount of power dissipated in a driver circuitmay be reduced through the use of a DC/DC regulator. For instance, anexternal DC/DC regulator, which may be electrically positioned betweenthe variable power source and the driver circuit, may generate acontinuous supply voltage from the variable power source and the drivercircuit may use the generated continuous supply voltage to provide powerto a load. In operation, the DC/DC regulator may reduce the amount ofpower dissipated in a driver circuit by preventing the supply voltagefrom reaching the “worst case” level.

In other examples, the amount of power dissipated in a driver circuitmay be reduced through the use of one or more passive components inseries with the load. For instance, one or more resistors and/or one ormore diodes may be placed in series with the load. In operation, the oneor more passive components may reduce the amount of power dissipated ina driver circuit by reducing the voltage drop across the driver circuit.

In other examples, the amount of power dissipated in a driver circuitmay be reduced through the use of one or more additional driver circuitsin parallel with the driver circuit. In operation, the use of one ormore additional driver circuits in parallel with the driver circuit mayreduce the amount of power dissipated in a driver circuit by reducingthe current level flowing through the driver circuit in proportion tothe number of additional driver circuits used. For example, if oneadditional driver circuit is used, the amount of power dissipated in thedriver circuit may be reduced by half.

In some examples, the above techniques for reducing power dissipationmay present one or more disadvantages. As one example, the abovetechniques may be not be cost effective in that additional activecomponents may be needed to handle “worst case” power distribution whichmay result in a cost adder that may be proportional to the extra powerneeded. As another example, the above techniques may require extradesign effort in that more design work may be needed, especially for theballast solutions, to consider topics such as stability and performanceat low battery level which may depend from load characteristics (e.g.total output current, harness on the output network, etc.).

In accordance with one or more techniques of this disclosure, one ormore external components may be placed in parallel with a driver deviceto reduce amount of power dissipated in the driver device. As oneexample, one or more resistors and one or more switches may be placed inparallel with a current source of a driver device. In operation, acurrent source of the driver device may generate a first portion of apower signal with a first current level and the one or more externalcomponents may generate a second portion of the power signal with asecond current level. The first portion of the power signal and thesecond portion of the power signal may be combined to form the powersignal (which may have a current level equal to the first current leveland the second current level) that is used to drive one or more loadelements. By placing the one or more external components in parallelwith the current source of the driver device, the amount of currentflowing through the driver device may be reduced without reducing theamount of current provided to the one or more load elements. Asdiscussed above, the amount of power dissipated by a driver device isproportional to the amount of current flowing through the driver device.Therefore, by placing the one or more external components in parallelwith the current source of the driver device, the amount of powerdissipated by the driver may be reduced without reducing the amount ofcurrent provided to the one or more load elements.

As discussed above, in some examples, the power source that supplies thedriver circuit may be a variable power source, such as a battery with anoperating voltage range of 8V to 18V. In some examples, the currentlevel of the second portion of the power signal generated by the one ormore external components may be proportional to the voltage of the powersource. For instance, the current level of the second portion of thepower signal generated by the one or more external components mayincrease as the voltage of the power source increases. However, in someexamples, it may be desirable for the current level of the overall powersignal (the combined first portion and second portion) to be independentof the voltage of the power source.

In accordance with one or more techniques of this disclosure, a driverdevice placed in parallel with one or more external componentsconfigured to reduce amount of power dissipated in the driver device maybe configured to adjust the current level of the first portion of thepower signal such that the current level of the overall power signal isindependent of the voltage of the power source. For instance, the driverdevice may adjust the amount of current provided by a current sourceincluded in the driver device based on the current level of the secondportion of the power signal that is generated by the one or moreexternal components

In some examples, it may be desirable to selectively activate/deactivatethe load driven by the power signal. For instance, where the loadincludes one or more light emitting diodes (LEDs), it may be desirableto turn the LEDs on and off. As one example, the load driven by thepower signal may be activated/deactivated by activating/deactivating thepower source that supplies the driver device. As another example, theload driven by the power signal may be activated/deactivated bydecoupling the power source that supplies the driver device from thedriver device. However, in some examples, it may be desirable toselectively activate/deactivate the load driven by the power signalwithout deactivating the driver device.

In accordance with one or more techniques of this disclosure, a driverdevice may be configured to selectively activate/deactivate the loaddriven by the power signal while still receiving power from a powersource. For instance, a driver device may selectively cause a currentsource of the driver device to cease generating the first portion of thepower signal and cause the one or more components to cease generatingthe second portion of the power signal. In some examples, a driverdevice may be configured to selectively activate/deactivate the loaddriven by the power signal based on a control signal received from anexternal device, such as a microcontroller.

FIGS. 1A-1D are a conceptual diagrams illustrating example systems thateach include a driver device configured to drive a load with a powersignal, in accordance with one or more exemplary techniques of thisdisclosure. As illustrated in FIGS. 1A-1D, each of systems 1A-1Dincludes a driver device 3 configured to drive a load 6 with a powersignal.

In some examples, systems 1A-1D may include a load 6, which may beconfigured to receive power from driver device 3. In some examples, load6 may include one or more light emitting devices (e.g., one or morelight bulbs, one or more light emitting diodes (LEDs), one or more laserdiodes, and the like), one or more batteries, one or more computingdevices, one or more resistive devices, one or more capacitive devices,one or more inductive devices, any other device that uses electricalpower, or any combination of the same. In one specific example, load 6may include one or more LEDs located on an automobile (e.g., headlights,fowlights, tail-lights, reverse lights, brake lights, turn signals, andthe like). As illustrated in FIGS. 1A-1D, load 6 may be connected suchthat driver device 3 may be a high-side driver with respect to load 6.

In some examples, systems 1A-1D may include a driver device 3, which maybe configured to control the amount of power provided to loads frompower sources. For instance, driver device 3 may control the amount ofpower provided to load 6 from a power source that supplies power signalV_(s). In some examples, the power source may be a variable powersource, such as a battery that supplies power signal V_(s) in a voltagerange of 8V to 18V. As the power dissipated by driver device 3 increasesin proportion to the voltage across driver device 3 and excess powerdissipation may negatively impact the functionality of driver device 3,it may be desirable for driver device 3 to be able to dissipate the“worst case” amount of power without negatively impacting thefunctionality of driver device 3. In the example of FIG. 1A, the powerdissipated by driver 3 may be determined in accordance with Equation(1), below.

P=(V _(s) −V _(Load))*I  (1)

As discussed above, it may be desirable to reduce the amount of powerdissipated in driver circuits, such as driver device 3 (e.g., to reducethe amount of power dissipated by the driver circuit in the “worstcase”). In accordance with one or more techniques of this disclosure andas shown in FIGS. 1B-1D, the amount of power dissipated in driver device3 may be reduced through the use of one or more passive components inseries with load 6. In the example of FIG. 1B, the amount of powerdissipated in driver device 3 may be reduced through the use of resistor8 in series with load 6. The power dissipated by driver 3 in the exampleof FIG. 1B may be determined in accordance with Equation (2), below.

P=(V _(s) −R*I−V _(Load))*I  (2)

In the example of FIG. 1C, the amount of power dissipated in driverdevice 3 may be reduced through the use of diodes 10A and 10B in serieswith load 6. The power dissipated by driver 3 in the example of FIG. 1Cmay be determined in accordance with Equation (3), below.

P=(V _(s)−2*V _(Diode) −V _(Load))*I  (3)

In the example of FIG. 1D, the amount of power dissipated in driverdevice 3 may be reduced through the use of zener diode 12 in series withload 6. The power dissipated by driver 3 in the example of FIG. 1D maybe determined in accordance with Equation (4), below.

P=(V _(s) −V _(zener) −V _(Load))*I  (4)

As can be seen from Equations (1)-(4), the amount of power dissipated indriver device 3 may be reduced through the use of one or more passivecomponents in series with load 6. However, in some examples, it may notbe desirable to use one or more passive components in series with load 6to reduce the amount of power dissipated in driver device 3.

FIG. 2 is a conceptual diagram illustrating an example system thatincludes a plurality of driver devices configured to collectively drivea load with a power signal, in accordance with one or more exemplarytechniques of this disclosure. As illustrated in FIG. 2, system 1Eincludes a driver device 3 and additional driver devices 5A-5N(collectively, “additional driver devices 5”) that are configured tocollectively drive a load 6 with a power signal.

In some examples, system 1E may include additional driver devices 5,which may be configured to perform operations similar to driver device3. For instance, additional driver devices 5 may be configured tocontrol the amount of power provided to load 6 from a power source thatsupplies power signal V_(s).

As discussed above, it may be desirable to reduce the amount of powerdissipated in driver circuits, such as driver device 3 (e.g., to reducethe amount of power dissipated by the driver circuit in the “worstcase”). In accordance with one or more techniques of this disclosure,the amount of power dissipated in driver device 3 may be reduced throughthe use of one or more additional driver devices 5 in parallel withdriver device 3. For instance, in the example of FIG. 2, the amount ofpower dissipated in driver device 3 may reduced in proportion to thenumber of driver devices included in additional driver devices 5. As oneexample, if additional driver devices 5 includes three driver devices,the amount of power dissipated in the driver circuit may be reduced byone-quarter (25%).

However, in some examples, it may not be desirable to use additionaldriver devices 5 in parallel with driver device 3 to reduce the amountof power dissipated in driver device 3. As one example, the use ofadditional driver devices 5 may increase a cost of system 1E. As anotherexample, the use of additional driver devices 5 may require extra designeffort.

FIG. 3 is a conceptual diagram illustrating an example system thatincludes a driver device and one or more passive elements configured tocollectively drive a load with a power signal, in accordance with one ormore exemplary techniques of this disclosure. As illustrated in FIG. 3,system 2A may include driver device 4A, load 6, and one or more passiveelements 16.

In some examples, system 2A may include driver device 4A, which may beconfigured to control and amount of power provided to a load. Forinstance, driver device 4A may be configured to generate a portion of apower signal that drives load 6. As shown in FIG. 3, driver 4A mayinclude current source 18, loop controller 20, shunt 22, and connectors24A-24C (collectively, “connectors 24”). In some examples, such as theexample of FIG. 3, driver device 4A may be a high-side driver withrespect to load 6. In some examples, such as the example of FIG. 4,driver device 4A may be a low-side driver with respect to load 6.

In some examples, driver device 4A may include current source 18, whichmay be configured to generate a power signal. For instance, currentsource 18 may generate a power signal with current level I_(CS), whichmay be a portion of the power signal that drives load 6. In someexamples, the current level of the power signal generated by currentsource 18 may be set by one or more other components, such as loopcontroller 20. In some examples, current source 18 may be a linearcurrent source.

As discussed above, while it may be generally desirable to reduce thepower dissipated by driver devices, it may not be desirable to achievethe reduction in power dissipation through the use of additional driverdevices in parallel or the use of passive components in series with thedriver devices. In accordance with one or more techniques of thisdisclosure, system 2A may include, one or more passive elements 16 thatare positioned in parallel to driver device 4A and may be configured togenerate a portion of a power signal that drives load 6. For instance,current source 18 may generate a first portion of a power signal thatdrives load 6 with a first current level (i.e., I_(CS)) and one or morepassive elements 16 may generate a second portion of the power signalthat drives load 6 with a second current level (i.e., I_(Pass)). Thefirst portion of the power signal and the second portion of the powersignal may be combined to create a total power signal that drives load 6and has a current level (i.e., I_(Total)) that is a sum of the firstcurrent level and the second current level. As all of the current of thepower signal is not flowing through current source 18 (e.g., because aportion of the current of the power signal is flowing through passiveelements 16 in parallel to current source 18), the amount of powerdissipated by current source 18 may be reduced.

In some examples, passive elements 16 may include one or more resistorsand the current level of the portion of the power signal generated bypassive elements 16 may be determined in accordance with Equation (5),where I_(Pass) is the current level of the portion of the power signalgenerated by passive elements 16, V_(Pass) is the voltage across passiveelements 16, and R_(Pass) is the resistance of passive elements 16.

$\begin{matrix}{I_{Pass} = \frac{V_{Pass}}{R_{Pass}}} & (5)\end{matrix}$

As discussed above, in some examples, the power source that suppliesdriver device 4A may be a variable power source, such as a battery withan operating voltage range of 8V to 18V. In some examples, the currentlevel of the second portion of the power signal generated by passiveelements 16 may be proportional to the voltage of the power source(i.e., V_(s)). For instance, the current level of the second portion ofthe power signal generated by passive elements 16 may increase as thevoltage of the power source increases. However, in some examples, it maybe desirable for the current level of the overall power signal (i.e.,I_(Total)) to be independent of the voltage of the power source.

In accordance with one or more techniques of this disclosure, in someexamples, driver device 4A may include loop controller 20, which may beconfigured to adjust a current level of the power signal generated bycurrent source 18. In some examples, loop controller 20 may adjust thecurrent level of the power signal generated by current source 18 basedon a current level of the power signal generated by passive elements 16.For instance, loop controller 20 may adjust the current level of thepower signal generated by current source 18 (i.e., I_(CS)) based on acurrent level of the power signal generated by passive elements 16(i.e., I_(Pass)) such that a total current level of the power signalthat drives load 6 (i.e., I_(Total)) is maintained at a particularcurrent level. In this way, loop controller 20 may enable the currentlevel of the overall power signal (i.e., I_(Total)) to be independent ofthe voltage of the power source.

As discussed above, it may be desirable to selectivelyactivate/deactivate a load, such as load 6, being driven by a driverdevice, such as driver 4A or 4B without deactivating the driver device(e.g., without disconnecting or decoupling the driver device from apower source). In some examples, loop controller 20 may selectivelyactivate/deactivate current source 18 in order to activate/deactivateload 6. However, in some examples, simply activating/deactivatingcurrent source 18 may be insufficient to activate/deactivate load 6. Forinstance, in the example of FIG. 3 where a portion of the power signalthat drives load 6 is generated by passive elements 16, simplyactivating/deactivating current source 18 may be insufficient toactivate/deactivate load 6 because load 6 may still receive power frompassive elements 16 even where current source 18 is deactivated.

In accordance with one or more techniques of this disclosure, driverdevice 4B may be configured to selectively activate/deactivate load 6 byboth selectively preventing current source 18 from generating the firstportion of the power signal and selectively preventing passive elements16 from generating the second portion of the power signal. In someexamples, driver device 4B may selectively prevent passive elements 16from generating the second portion of the power signal byopening/closing a switch positioned in series with passive elements 16.As such, in some examples, driver device 4B may include a controlterminal via which driver device 4B may output a signal to selectivelyprevent passive elements 16 from generating the second portion of thepower signal. Further details of some example driver devices that mayselectively prevent passive elements from generating the second portionof the power signal are discussed below with reference to FIGS. 5 and 6.

FIG. 5 is a conceptual diagram illustrating an example system 4C thatincludes a driver device and one or more passive elements configured tocollectively drive a load with a power signal, in accordance with one ormore exemplary techniques of this disclosure. As illustrated in FIG. 5,system 2C may include driver device 4C, load 6, switch 28, and one ormore passive elements 16.

In some examples, system 2C may include driver device 4C, which may beconfigured to perform operations similar to driver device 4A of FIG. 3.For instance, driver device 4C may be configured to generate a portionof a power signal that drives load 6.

In accordance with one or more techniques of this disclosure, driverdevice 4C may be configured to selectively activate/deactivate load 6 byboth selectively preventing current source 18 from generating the firstportion of the power signal and selectively preventing passive elements16 from generating the second portion of the power signal. In someexamples, driver device 4C may selectively prevent passive elements 16from generating the second portion of the power signal byopening/closing a switch positioned in series with passive elements 16,such as switch 28. As illustrated in FIG. 5, switch 28 may include aPMOS switch.

In one example operation, switch 28 may be closed, driver 4C maygenerate a first portion of a power signal used to drive load 6 andpassive elements 16 may generate a second portion of the power signal.Driver 4C may receive a control signal from an external device, such asa microcontroller, that causes driver 4C to deactivate load 6. Inresponse to the control signal, loop controller 20 may prevent currentsource 18 from generating the first portion of the power signal andswitch 30 may open. The opening of switch 30 may cause switch 28 tocease allowing current to flow through passive elements 16. In this way,driver device 4C may be configured to selectively activate/deactivateload 6 without being disconnected or decoupled from V_(s).

FIG. 6 is a conceptual diagram illustrating an example system 4D thatincludes a driver device and one or more passive elements configured tocollectively drive a load with a power signal, in accordance with one ormore exemplary techniques of this disclosure. As illustrated in FIG. 6,system 2D may include driver device 4D, load 6, switch 28, and one ormore passive elements 16. However, as opposed to the example of FIG. 5where switch 28 is illustrated as a PMOS switch, FIG. 6 illustrates anexample where switch 28 includes an NMOS switch. In some examples, theuse of an NMOS switch may be desirable over a PMOS switch. For instance,NMOS switches may be cheaper than PMOS switches.

In some examples, system 2D may include driver device 4D, which may beconfigured to perform operations similar to driver device 4C of FIG. 4.For instance, driver device 4D may be configured to selectivelyactivate/deactivate load 6 by both selectively preventing current source18 from generating the first portion of the power signal and selectivelypreventing passive elements 16 from generating the second portion of thepower signal. However, as opposed to driver device 4C which isconfigured to operate switch 28 as a PMOS switch, driver device 4D isconfigured to operate switch 28 as an NMOS switch.

Referring to both FIGS. 5 and 6, the resistances the resistors includedin passive elements 16 may be selected to minimize the power dissipatedby switch 28. Specifically, if the resistances the resistors included inpassive elements 16 are properly dimensioned, the power dissipated byswitch 28 may be negligible in nearly all conditions (i.e., operative),especially if the conductance of switch 28 (gm) is high at lowgate-source voltage (V_(gs)) levels. As such, in some examples, switch28 may comprise a relatively high-ohmic MOS in a small non-exposedpackage. For instance, in examples where load 6 includes LEDs used onthe rear of an automobile, switch 28 may comprise a relativelyhigh-ohmic MOS in a small non-exposed package while still complying witha typical power budget for the rear light LED arena.

FIG. 7 is a graph 700 illustrating example current levels in a systemthat includes a driver device and one or more passive elementsconfigured to collectively drive a load with a power signal, inaccordance with one or more exemplary techniques of this disclosure. Asillustrated in FIG. 7, graph 700 includes a horizontal x-axis indicatinga voltage level, a vertical y-axis indicating a current level, firstplot 702 representing a first voltage/current relationship, second plot704 representing a second voltage/current relationship, and third plot706 representing a third voltage/current relationship. In some examples,first plot 702 may represent the voltage/current relationship for thefirst portion of the power signal generated by current source 18 ofdriver device 4 of system 2 of FIGS. 3-6 (i.e., I_(CS)), second plot 704may represent the voltage/current relationship for the second portion ofthe power signal generated by passive elements 16 of system 2 of FIGS.3-6 (i.e., I_(Pass)), and third plot 706 may represent thevoltage/current relationship for the total power signal used to driveload 6 of system 2 of FIGS. 3-6 (i.e., I_(Total)).

As discussed above, it may be desirable for the current level of theoverall power signal (i.e., I_(Total)) to be independent of the voltageof the power source. In accordance with one or more techniques of thisdisclosure, loop controller 20 of driver device 4 may adjust a currentlevel of the power signal generated by current source 18 (i.e., I_(CS))based on a current level of the power signal generated by passiveelements 16 (i.e., I_(Pass)) such that a total current level of thepower signal that drives load 6 (i.e., I_(Total)) is maintained at aparticular current level. As shown by graph 700, as the current level ofthe power signal generated by passive elements 16 (i.e., I_(Pass))changes, loop controller 20 may adjust the current level of the powersignal generated by current source 18 (i.e., I_(CS)) such that the totalcurrent level of the power signal that drives load 6 (i.e., I_(Total))is maintained at a particular current level.

In some examples, loop controller 20 may perform the adjustment suchthat the total current level of the power signal that drives load 6(i.e., I_(Total)) is maintained at a particular current level within aparticular voltage range. For instance, where load 6 comprises one ormore LEDs that have a forward activation voltage level (i.e., V_(fLED))708 and a voltage level of the power source of driver device 4 (i.e., V)is voltage level 710, loop controller 20 may perform the adjustment suchthat the total current level of the power signal that drives load 6(i.e., I_(Total)) is maintained between voltage level 708 and voltagelevel 710. In this way, loop controller 20 may enable the current levelof the overall power signal (i.e., 1, t) to be independent of thevoltage of the power source across the entire operational range of load6.

FIG. 8 is a conceptual diagram illustrating an example system 2E thatincludes a multi-channel driver device and a plurality of passiveelements configured to collectively drive a plurality of loads with aplurality of power signals, in accordance with one or more exemplarytechniques of this disclosure. As illustrated in FIG. 8, system 2E mayinclude driver device 4E, one or more loads 6A-6N (collectively, “loads6”), and one or more sets of passive elements 16A-16N (collectively,“passive element sets 16”).

In some examples, system 2E may include driver device 4E, which may beconfigured to perform operations similar to driver device 4A of FIG. 3,driver device 4B of FIG. 4, driver device 4C of FIG. 5, and/or driverdevice 4D of FIG. 6. For instance, driver device 4E may be configured togenerate a portion of a power signal that drives a load. However, asshown in FIG. 8, driver device 4E may be a multi-channel driver devicewhich may simultaneously generate respective portions of respectivepower signals that each drive a respective load of loads 6. Forinstance, each of current sources 18A-18N (collectively “current sources18”) may generate a respective first portion of a respective powersignal that drives a respective load of loads 6. Similarly, each ofpassive element sets 16 may generate a respective second portion of arespective power signal that drives a respective load of loads 6. As oneexample, current source 18A may generate a first portion of a powersignal with current level I_(CS) _(_) _(A), passive elements 16A maygenerate a second portion of the power signal with current levelI_(PASS) _(_) _(A), and the first and second portions of the powersignal may be combined to generate a total power signal with currentlevel I_(Total) _(_) _(A) that drives load 6A. As another example,current source 18B may generate a first portion of a power signal withcurrent level I_(CS) _(_) _(B), passive elements 16B may generate asecond portion of the power signal with current level I_(PASS) _(_)_(B), and the first and second portions of the power signal may becombined to generate a total power signal with current level I_(Total)_(_) _(B) that drives load 6B.

In accordance with one or more techniques of this disclosure, driverdevice 4E may be configured to selectively activate/deactivate loads 6by both selectively preventing current sources 18 from generatingrespective first portions of the power signals and selectivelypreventing respective passive elements of passive elements 16A-16N fromgenerating respective second portions of the power signals.

FIG. 9 is a schematic diagram illustrating an example load 6 that may bedriven using a power signal generated by a driver device and one or morepassive elements in parallel with the driver device, in accordance withone or more techniques of this disclosure. As discussed above, load 6may include one or more LEDs located on an automobile (e.g., headlights,fowlights, tail-lights, reverse lights, brake lights, turn signals, andthe like). In some examples, it may be desirable to drive a more thanone LED with a single driver device. For instance, as shown in theexample of FIG. 8, load 6 may include an array of LEDs. In exampleswhere load 6 includes a plurality of LEDs (in an array, in series, inparallel), the current requirements of load 6 may increase as comparedto examples where load 6 includes a single LED. As the currentrequirements of load 6 increase, the power dissipated by the driverdevice, such as driver device 4, may correspondingly increase. Asdiscussed above and in accordance with one or more techniques of thisdisclosure, the power dissipation of a current source of a driver devicemay be reduced through the use of one or more passive elements inparallel with the current source that generate a portion of the powersignal used to drive the load.

FIG. 10 is a flow diagram illustrating an example technique reducing thepower dissipation of a driver device, in accordance with one or moretechniques of this disclosure. For purposes of illustration only, theexample operations are described below within the context of driverdevice 4, as shown in FIGS. 3-6, though driver devices other than driverdevice 4 may perform the techniques of FIG. 10.

In accordance with one or more techniques of this disclosure, driverdevice 4 may generate a first portion of a power signal (1002). Forinstance, current source 18 of driver device 4 may generate a portion ofa power signal that drives load 6. In some examples, the current levelof the portion of the power signal that is generated by current source18 may be denoted as I_(CS).

Driver device 4 may determine a current level of a second portion of thepower signal that is generated by one or more passive components (1004).For instance, loop controller 20 of driver device 4 may determine acurrent level of a portion of the power signal that is generated bypassive elements 16 of FIGS. 3-6. In some examples, loop controller 20may determine the current level of the portion of the power signal thatis generated by passive elements 16 based on a voltage across a senseresistor, such as shunt 22. In some examples, the sense resistor may beincluded within driver device 4. In some example, the sense resistor maybe external to driver device 4. In some examples, the current level ofthe portion of the power signal that is generated by passive components16 may be denoted as I_(Pass).

Driver device 4 may adjust a current level of the first portion of thepower signal based on the current level of the second portion of thepower signal (1006). For instance, loop controller 20 may adjust acurrent level of the power signal generated by current source 18 (i.e.,I_(CS)) based on the current level of the power signal generated bypassive elements 16 (i.e., I_(Pass)) such that a total current level ofthe power signal that drives load 6 (i.e., I_(Total)) is maintained at aparticular current level. In this way, the power dissipation of driverdevice 4 may be reduced without changing the characteristics (i.e.,current level) of the power signal that drives load 6.

The following numbered examples may illustrate one or more aspects ofthe disclosure:

Example 1

A method comprising: generating, by a current source of a device, afirst portion of a power signal that drives one or more load elements,wherein a second portion of the power signal is generated by one or morecomponents that are external to the device and are in parallel to thecurrent source such that the second portion of the power signal does notflow through the current source.

Example 2

The method of example 1, further comprising: adjusting, by the deviceand based on a current level of the second portion of the power signal,a current level of the first portion of the power signal to maintain atotal current level of the power signal.

Example 3

The method of any combination of examples 1-2, further comprising:preventing, based on a control signal received from an external device,the current source from generating the first portion of the power signaland the one or more components from generating the second portion of thepower signal.

Example 4

The method of any combination of examples 1-3, wherein preventing theone or more components from generating the second portion of the powersignal comprises: opening a switch positioned in series with the one ormore components.

Example 5

The method of any combination of examples 1-4, wherein the one or morecomponents are not active current sources.

Example 6

The method of any combination of examples 1-5, wherein the one or morecomponents comprise one or more resistors.

Example 7

The method of any combination of examples 1-6, wherein the one or moreload elements comprise one or more light emitting diodes (LEDs).

Example 8

A driver device comprising: a current source configured to generate afirst portion of a power signal that drives one or more load elements,wherein a second portion of the power signal is generated by one or morecomponents that are external to the device and are in parallel to thecurrent source such that the second portion of the power signal does notflow through the current source.

Example 9

The driver device of example 8, further comprising: a loop controllerconfigured to adjust, based on a current level of the second portion ofthe power signal, a current level of the first portion of the powersignal to maintain a total current level of the power signal.

Example 10

The driver device of any combination of examples 8-9, wherein, based ona control signal received from an external device, the loop controlleris configured to prevent the current source from generating the firstportion of the power signal and prevent the one or more components fromgenerating the second portion of the power signal.

Example 11

The driver device of any combination of examples 8-10, wherein, toprevent the one or more components from generating the second portion ofthe power signal, the loop controller is configured to: open a switchpositioned in series with the one or more components.

Example 12

The driver device of any combination of examples 8-11, wherein the oneor more components are not active current sources.

Example 13

The driver device of any combination of examples 8-12, wherein the oneor more components comprise one or more resistors.

Example 14

The driver device of any combination of examples 8-13, wherein the oneor more load elements comprise one or more light emitting diodes (LEDs).

Example 15

A driver device comprising: means for generating a first portion of apower signal that drives one or more load elements, wherein a secondportion of the power signal is generated by one or more components thatare external to the device and are in parallel to the current sourcesuch that the second portion of the power signal does not flow throughthe current source; and means for outputting the first portion of thepower signal.

Example 16

The driver device of example 15, further comprising: means foradjusting, based on a current level of the second portion of the powersignal, a current level of the first portion of the power signal tomaintain a total current level of the power signal.

Example 17

The driver device of any combination of examples 15-16, furthercomprising: means for combining the first portion and the second portionto generate the power signal, wherein the means for outputting comprisemeans for outputting the power signal.

Example 18

The driver device of any combination of examples 15-17, furthercomprising: means for preventing, based on a control signal receivedfrom an external device, the means for generating from generating thefirst portion of the power signal and the one or more components fromgenerating the second portion of the power signal.

The techniques described in this disclosure may be implemented, at leastin part, in hardware, software, firmware, or any combination thereof.For example, various aspects of the described techniques may beimplemented within one or more processors, including one or moremicroprocessors, digital signal processors (DSPs), application specificintegrated circuits (ASICs), field programmable gate arrays (FPGAs), orany other equivalent integrated or discrete logic circuitry, as well asany combinations of such components. The term “processor” or “processingcircuitry” may generally refer to any of the foregoing logic circuitry,alone or in combination with other logic circuitry, or any otherequivalent circuitry. A control unit including hardware may also performone or more of the techniques of this disclosure.

Such hardware, software, and firmware may be implemented within the samedevice or within separate devices to support the various techniquesdescribed in this disclosure. In addition, any of the described units,modules, or components may be implemented together or separately asdiscrete but interoperable logic devices. Depiction of differentfeatures as modules or units is intended to highlight differentfunctional aspects and does not necessarily imply that such modules orunits must be realized by separate hardware, firmware, or softwarecomponents. Rather, functionality associated with one or more modules orunits may be performed by separate hardware, firmware, or softwarecomponents, or integrated within common or separate hardware, firmware,or software components.

The techniques described in this disclosure may also be embodied orencoded in an article of manufacture including a computer-readablestorage medium encoded with instructions. Instructions embedded orencoded in an article of manufacture including a computer-readablestorage medium encoded, may cause one or more programmable processors,or other processors, to implement one or more of the techniquesdescribed herein, such as when instructions included or encoded in thecomputer-readable storage medium are executed by the one or moreprocessors. Computer readable storage media may include random accessmemory (RAM), read only memory (ROM), programmable read only memory(PROM), erasable programmable read only memory (EPROM), electronicallyerasable programmable read only memory (EEPROM), flash memory, a harddisk, a compact disc ROM (CD-ROM), a floppy disk, a cassette, magneticmedia, optical media, or other computer readable media. In someexamples, an article of manufacture may include one or morecomputer-readable storage media.

In some examples, a computer-readable storage medium may include anon-transitory medium. The term “non-transitory” may indicate that thestorage medium is not embodied in a carrier wave or a propagated signal.In certain examples, a non-transitory storage medium may store data thatcan, over time, change (e.g., in RAM or cache).

Various aspects have been described in this disclosure. These and otheraspects are within the scope of the following claims.

1. A method comprising: generating, by a current source of a device, afirst portion of a power signal that drives one or more load elements,wherein a second portion of the power signal is generated by one or morecomponents that are external to the device and are in parallel to thecurrent source such that the second portion of the power signal does notflow through the current source.
 2. The method of claim 1, furthercomprising: adjusting, by the device and based on a current level of thesecond portion of the power signal, a current level of the first portionof the power signal to maintain a total current level of the powersignal.
 3. The method of claim 1, further comprising: preventing, basedon a control signal received from an external device, the current sourcefrom generating the first portion of the power signal and the one ormore components from generating the second portion of the power signal.4. The method of claim 3, wherein preventing the one or more componentsfrom generating the second portion of the power signal comprises:opening a switch positioned in series with the one or more components.5. The method of claim 3, wherein the one or more components are notactive current sources.
 6. The method of claim 1, wherein the one ormore components comprise one or more resistors.
 7. The method of claim1, wherein the one or more load elements comprise one or more lightemitting diodes (LEDs).
 8. A driver device comprising: a current sourceconfigured to generate a first portion of a power signal that drives oneor more load elements, wherein a second portion of the power signal isgenerated by one or more components that are external to the device andare in parallel to the current source such that the second portion ofthe power signal does not flow through the current source.
 9. The driverdevice of claim 8, further comprising: a loop controller configured toadjust, based on a current level of the second portion of the powersignal, a current level of the first portion of the power signal tomaintain a total current level of the power signal.
 10. The driverdevice of claim 8, wherein, based on a control signal received from anexternal device, the loop controller is configured to prevent thecurrent source from generating the first portion of the power signal andprevent the one or more components from generating the second portion ofthe power signal.
 11. The driver device of claim 10, wherein, to preventthe one or more components from generating the second portion of thepower signal, the loop controller is configured to: open a switchpositioned in series with the one or more components.
 12. The driverdevice of claim 10, wherein the one or more components are not activecurrent sources.
 13. The driver device of claim 8, wherein the one ormore components comprise one or more resistors.
 14. The driver device ofclaim 8, wherein the one or more load elements comprise one or morelight emitting diodes (LEDs).
 15. A driver device comprising: means forgenerating a first portion of a power signal that drives one or moreload elements, wherein a second portion of the power signal is generatedby one or more components that are external to the device and are inparallel to the current source such that the second portion of the powersignal does not flow through the current source; and means foroutputting the first portion of the power signal.
 16. The driver deviceof claim 15, further comprising: means for adjusting, based on a currentlevel of the second portion of the power signal, a current level of thefirst portion of the power signal to maintain a total current level ofthe power signal.
 17. The driver device of claim 16, further comprising:means for combining the first portion and the second portion to generatethe power signal, wherein the means for outputting comprise means foroutputting the power signal.
 18. The driver device of claim 15, furthercomprising: means for preventing, based on a control signal receivedfrom an external device, the means for generating from generating thefirst portion of the power signal and the one or more components fromgenerating the second portion of the power signal.